There’s a Reason Honda Made Active Exhaust, Don’t Disable

[GJPEN]

I just did the active exhaust disable (everything else is stock)and I have to say there is much more bad than good with this. Here are my impressions on the positive and negative and ymmv. Curious if anyone else has seen these negatives? I may try an Air filter or tune, but I don’t want to mess with the mid range power delivery curve.

Positive - Idle, is deeper and more delineated sound between the cylinders firing

Negative - The power band from 2k -4.5k is much less “elastic”. It may be faster but the power delivery is less exciting and predictable for judging power through curves or traffic.Less fun.

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[spectre186]

Placebo effect. If it was a legit concern all aftermarket exhausts would keep the factory valve. We would also see people post dyno plots if there was a noticeable difference.

 

[Jester04]

Placebo effect. If it was a legit concern all aftermarket exhausts would keep the factory valve. We would also see people post dyno plots if there was a noticeable difference.

Agree, I run mine with the valve open all the time and 0 issues.

 

[Clark_Kent]

It may be helpful for you to review this thread in its entirety. It starts to get interesting on Page 4. @Jester04 I recall you mentioning you would share data on Exhaust Valvegate once you received Hondata. Any update on this?

 

[AZCWTypeR]

I just did the active exhaust disable (everything else is stock)and I have to say there is much more bad than good with this. Here are my impressions on the positive and negative and ymmv. Curious if anyone else has seen these negatives? I may try an Air filter or tune, but I don’t want to mess with the mid range power delivery curve.

Positive - Idle, is deeper and more delineated sound between the cylinders firing

Negative - The power band from 2k -4.5k is much less “elastic”. It may be faster but the power delivery is less exciting and predictable for judging power through curves or traffic.Less fun.

Mine is now 100% open and no difference in drivability. I live in AZ however.

I suspect the valve is there strictly for noise emissions, which are strict in some countries and reportedly the main reason Porsche 911's became water cooled (air cooling fins resonated noise along with the cooling fan).

I know OEM motorcycle tuning is strongly influenced by noise emissions and custom fuel/timing maps often boost midrange the most, and ignoring the noise restriction at cruise speeds.

 

[GJPEN]

I really don't think its placebo effect. I have gone back and forth with the fuse out and back in I really wanted to like the valve open all the time.

Thanks for that thread. I am by no means an expert at tuning but I am pretty sensitive to changes there is defiantly something different with how the car accelerates in the mid range rpm. There has to be a change in the response or at least the feeling? Someone has to notice something here besides me. Again my car is totally stock so that may be hard.

My hunch is the valve is closed on low rpm and then opens and it "spools" out in a more elastic fashion, in the 2-4.5k rpm range when hitting the gas. the valve open all the time to me actually seems like there is a little more guts but it isn't as dramatic as pulling with it on. A more "flat" pull.

 

[Noize]

I really don't think its placebo effect. I have gone back and forth with the fuse out and back in I really wanted to like the valve open all the time.

Thanks for that thread. I am by no means an expert at tuning but I am pretty sensitive to changes there is defiantly something different with how the car accelerates in the mid range rpm. There has to be a change in the response or at least the feeling? Someone has to notice something here besides me. Again my car is totally stock so that may be hard.

My hunch is the valve is closed on low rpm and then opens and it "spools" out in a more elastic fashion, in the 2-4.5k rpm range when hitting the gas. the valve open all the time to me actually seems like there is a little more guts but it isn't as dramatic as pulling with it on. A more "flat" pull.

Put it on a dyno and prove it. Otherwise, it’s just an armchair theory. You can’t equate truth to feel.

 

[Jester04]

It may be helpful for you to review this thread in its entirety. It starts to get interesting on Page 4. @Jester04 I recall you mentioning you would share data on Exhaust Valvegate once you received Hondata. Any update on this?

Sorry forgot to post about it.

Stock exhaust valve values respectively for
Comfort
Sport
R+

Dyno testing on my stock car with just an intercooler and valve completely open showed peak torque at around 3,300-3600 rpms starting the pulls at around 2,200 rpms. The valve opens half way at 2300rpms in R+ and shortly after it opens up completely.

So there is literally no way the valve is closed during spool up unless you are lugging the engine in 6th gear at like 1500rpms.

I will gladly give a discounted tuning price for whoever has a stock turbo car that is willing to dyno the car. To test this theory out, I can no longer try it out since I don’t have a stock turbo anymore.

I will close your valve on a pull and then one with fully open.

Here is the log for the dyno on my car on stock turbo with no mods aside from intercooler. The valve is already halfway open already in the programming and it still has not built boost. Even though I had my valve open it still applies that the valve is already bypassing most of the exhaust gas through the center section.

 

[getGroyped]

What’s the reason for Honda creating the active exhaust? I don’t know for sure, but I suspect it’s for better an emissions or MPG score to “save the planet”. I’m leaving mine open.

 

[Jester04]

What’s the reason for Honda creating the active exhaust? I don’t know for sure, but I suspect it’s for better an emissions or MPG score to “save the planet”. I’m leaving mine open.

So I can’t 100% sure say the reason for the valve. From all I have seen in datalogs, in the software and the logic behind of when it opens. It leads me to believe it’s there for marginal performance reasons. Just to facilitate exhaust gases escaping and going through a single muffler instead of 2. That is the extent of it.

Until I can test it on the dyno won’t be able to say more sadly. But hopefully this can help clear some stuff up and the reason for my thoughts.

But the K20C is not a unicorn engine that uses black magic to defy the laws of physics. It’s an air pump just like every other engine out there at its core. If they can run without valves this one can too.

 

[CTR]

You weren't the only one to notice a difference.

My complaints about the valve being open all the time were during low rpm and partial throttle situations. Mostly during cold starts. I was called crazy for thinking the valve served any other purpose than noise...

I actually think it's kind of cool that the valve opens and closes. My brother-in-law could tell when he was driving behind me it was opening and closing and he's not really a car guy.

I don't think a dyno will really prove anything unless you're going to test in various load conditions and throttle positions. I would expect that it makes zero difference at wide open throttle and in boost as this is when Honda tells the valve to start opening anyway.

 

[scuderia_miso]

I used to have a turbocharged Accord that had an exhaust cutout routed to the stock ~2" exhaust and when the cutout was open it would run an open 3" downpipe. Basically the 2 extremes for exhaust flow.

One thing I observed was the open downpipe setup had amazing midrange and top end turbo response but the transient throttle response wasn't great in low RPM conditions, basically below 2000 RPM or so.

The stock exhaust was the exact opposite with the cutout closed. Transient response up to about 2000 RPM was good but everything above that sucked.

Obviously no data behind this but I am speculating it could be to improve transient throttle response at low RPM but also get the flow the turbo needs once it gets spinning. This theory seems to align with how Honda programmed it to open and close.

 

[Bazgab]

What’s the reason for Honda creating the active exhaust? I don’t know for sure, but I suspect it’s for better an emissions or MPG score to “save the planet”. I’m leaving mine open.

I really doubt it would create any difference in those areas (emissions/MPG). My guess - it is purely that some markets have stricter sound restrictions and then the MFG can use it as a marketing tool in areas without those stricter sound restrictions.

 

[Jester04]

You weren't the only one to notice a difference.

My complaints about the valve being open all the time were during low rpm and partial throttle situations. Mostly during cold starts. I was called crazy for thinking the valve served any other purpose than noise...

I actually think it's kind of cool that the valve opens and closes. My brother-in-law could tell when he was driving behind me it was opening and closing and he's not really a car guy.

I don't think a dyno will really prove anything unless you're going to test in various load conditions and throttle positions. I would expect that it makes zero difference at wide open throttle and in boost as this is when Honda tells the valve to start opening anyway.

The part throttle stuff would be difficult to test in R+ mode since the valve opens really early.

Probably in comfort it would be the best bet but I can actually force the car to run with the valve close if I wanted and really test it. I personally drive my car in individual mode with the suspension in comfort and engine sound, steering in sport and everything else R+.

But I know we all have our preferences.

 

[CTR]

The part throttle stuff would be difficult to test in R+ mode since the valve opens really early.

Probably in comfort it would be the best bet but I can actually force the car to run with the valve close if I wanted and really test it. I personally drive my car in individual mode with the suspension in comfort and engine sound, steering in sport and everything else R+.

But I know we all have our preferences.

You would know better than me but it was my understanding the valve functions the same in all engine modes and is based on load, RPM, and throttle position only. I think it was AWE that stated they found this in their exhaust testing.

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